The effect of soil type and degree of metal contamination upon uptake of Cd,Pb and Cu in bush beans (Phaseolus vulgaris L.)

Summary Five soils of increasing specific surface area (SSA) were loaded to five levels of contamination with Cd, Pb and Cu, and bean plants (Phaseolus vulgaris L.) were grown on the soils for 30 days. A linear correlation was found between the concentration of Cd in the soil solutions and the amount absorbed by the plant per gram root material for four out of the five soils, and, in the case of Cu, for all five soils. Quantitatively, there was insufficient Cd or Cu in the soil solution to account for plant uptake of these metals. The amount of Cd absorbed by plants could also be related to the adsorption density (concentration/SSA soil) of the metal in four of the five soils, whereas the Cu content of plants could be related to the adsorption density of all five soils. It is thought that the metals were removed from the soil solution by root absorption and replenished by metal cations adsorbed onto surface sites in the soil. Consideration of the adsorption density of these metals in the soil may be a useful means to determine the permissible limits for heavy metal application for a wide range of soils. Lead uptake was significantly correlated to total Pb in soils, but not to the adsorption density or soil solution concentrations. The possible interpretation of the results are discussed.